An onboard hydrogen generator for hydrogen enhanced combustion with internal combustion engine

Hydrogen enhanced combustion (HEC) for internal combustion engine is known to be a simple mean for improving engine efficiency in fuel saving and cleaner exhaust. An onboard compact and high efficient methanol steam reformer is made and installed in the tailpipe of a vehicle to produce hydrogen continuously onboard by using the waste heat of the engine for heating up the reformer; this provides a practical device for the HEC to become a reality. This use of waste heat from engine enables an extremely high process efficiency of 113% to convert methanol (8.68 MJ) for 1.0 NM of hydrogen (9.83 MJ) and low cost of using hydrogen as an enhancer or as a fuel itself. The test results of HEC from the onboard hydrogen production are presented with 2 gasoline engine vehicles and 2 diesel engines; the results indicate a hike of engine efficiency in 15–25% fuel saving and a 40–50% pollutants reduction including 70% reduction of exhaust smoke. The use of hydrogen as an enhancer brings about 2–3 fold of net reductions in energy, carbon dioxide emission and fuel cost expense over the input of methanol feed for hydrogen production.     

Recent advances in biomedical polyurethane biostability and biodegradation

This paper summarizes our recent efforts to better understand the effects of antioxidants, the effects of strain-state, mechanistic studies of soft segment cleavage by reactive oxygen radicals, and the effects of different soft segment chemistries on the biostability/biodegradation of polyether polyurethanes (PEUUs). In vivo cage implant system studies and in vitro cobalt ion/hydrogen peroxide studies have been carried out on PEUUs and the polymers have been analysed by attenuated total reflectance and Fourier transform infrared (ATR-FTIR) spectroscopy, and scanning electron microscopic (SEM) characterization of the PEUU surfaces. The natural antioxidant, vitamin E, has been shown to inhibit biodegradation and enhance biostability of PEUUs. Studies of the effect of stress state on PEUU biodegradation demonstrate that stress can inhibit biodegradation. While polyether soft segments may be cleaved by the presence of reactive oxygen radicals, the presence of oxygen has a profound effect in accelerating biodegradation. The biodegradation of polyurethanes may be inhibited by substituting different chemistries such as polydimethylsiloxanes, polycarbonates, and hydrocarbon soft segments for the polyether soft segments. To safely utilize polyurethanes in long-term biomedical devices, the biodegradation mechanisms of polyurethane elastomers must be fully understood and subsequently prevented. © 1998 SCI.     

Priority Scheduling of Transactions in Distributed Real-Time Databases

One of the most important issues in the design of distributed real-time database system (DRTDBS) is transaction scheduling which consists of two parts: priority scheduling and real-time concurrency control. In the past studies, mostly, these issues are studied separately although they have a very close interaction with each other. In this paper, we propose new priority assignment policies for DRTDBS and study their impact on two typical real-time concurrency control protocols (RT-CCPs), High Priority Two Phase Locking (HP-2PL) and Optimistic Concurrency Control with Broadcast Commit (OCC-BC). Our performance results show that many factors, such as data conflict resolution, degree of data contention and transaction restarts, that are unique to database systems, have significant impact on the performance of the policies which in turn affect the performance of the real-time concurrency control protocols. OCC-BC is more affected by the priority assignment policies than HP-2PL owing to the late detection of conflict. In the design of priority assignment policies, we have found that neither the purely deadline driven policies nor data contention driven policies are suitable for DRTDBS. Our proposed policy, the Mixed Method (MM), which considers both transaction timeliness and data contention, outperforms other policies over a wide range of system parameter settings.     

山梨酸钾对魔芋葡甘聚糖/玉米醇溶蛋白复合膜的性能和抑菌效果的影响

本文以魔芋葡甘聚糖和玉米醇溶蛋白为基材,制备了不同山梨酸钾添加量的复合膜,研究了复合膜的理化性能和抑菌效果。结果表明,添加不同含量山梨酸钾对复合膜的膜厚没有显著影响(p>0.05),复合膜的水蒸气透过率和透光性随着山梨酸钾添加量的增加而降低。复合膜的断裂伸长率随着山梨酸钾添加量的增加而显著增大(p<0.05),当其含量为12%时,复合膜的断裂伸长率为36.02%,是未添加山梨酸钾复合膜的1倍;当添加6%的山梨酸钾时,复合膜的拉伸强度最大,为58.78 MPa。随着山梨酸钾添加量的增加,复合膜对大肠杆菌、金黄色葡萄球菌和蜡样芽孢杆菌的抑菌效果明显增强。当山梨酸钾添加量为12%时,鱼肉在4℃储藏时的货架期可延长4 d。复合膜适合应用在食品保鲜包装。      

魔芋葡甘聚糖基可食膜的成膜机理研究进展

魔芋葡甘聚糖(KGM)是魔芋的主要成分,是目前发现的最优良的可溶性膳食纤维之一,由于其良好的成膜性,在食品包装领域有很好的应用前景。研究发现,KGM可与多糖、蛋白等进行不同方式和不同程度的混合,形成特殊的共混体系,干燥后可得到KGM基可食膜。本文就KGM结构和KGM基可食膜的成膜机理进行综述,以期为后续研究与应用提供一定参考。     

预混天然气小尺度燃烧特性的CFD研究

运用计算流体力学（CFD）二维模型研究预混天然气在小尺度空间内燃烧及墙壁的导热系数、外部的热损对燃烧特性的影响。研究表明,墙壁的导热系数和外壁面的热损直接影响着火焰的点燃、稳定及氮氧化物的生成。对于预混气体。仅存在一个很小的流速区间能维持通道内的燃烧。最后分析了轴向及径向的温度梯度对燃烧器的影响,找到了在模拟条件下最佳的热力条件,并以此达到优化小尺寸燃烧器的目的。     

Study of LiFePO4 cathode materials coated with high surface area carbon

LiFePO₄ is a potential cathode material for 4 V lithium-ion batteries. Carbon-coated lithium iron phosphates were prepared using a high surface area carbon to react precursors through a solid-state process, during which LiFePO₄ particles were embedded in amorphous carbon. The carbonaceous materials were synthesized by the pyrolysis of peanut shells under argon, where they were carbonized in a two-step process that occurred between 573 and 873 K. The shells were also treated with a proprietary porogenic agent with the goal of altering the pore structure and surface area of the pyrolysis products. The electrochemical properties of the as-prepared LiFePO₄/C composite cathode materials were systematically characterized by X-ray diffraction, scanning electron microscope, element mapping, energy dispersive spectroscopy, Raman spectroscopy, and total organic carbon (TOC) analysis. In LiFePO₄/C composites, the carbon not only increases rate capability, but also stabilizes capacity. In fact, the capacity of the composites increased with the specific surface area of carbon. The best result was observed with a composite made of 8.0 wt.% with a specific surface area of 2099 m² g⁻¹. When high surface area carbon was used as a carbon source to produce LiFePO₄, overall conductivity increased from 10⁻⁸ to 10⁻⁴ S cm⁻¹, because the inhibition of particle growth during the final sintering process led to greater specific capacity, improved cycling properties and better rate capability compared to a pure olivine LiFePO₄ material.     

Reflow soldering and isothermal solid-state aging of Sn-Ag eutectic solder on Au/Ni surface finish

The reaction between the eutectic Sn-3.5Ag solder and the Au/Ni surface finish during reflow as well as during isothermal aging was studied. The Au layer was electroplated and had a thickness of the one μm. The peak reflow temperature was fixed at 250 C while the reflow time was varied between 10 sec and one h. Samples that went through 90 sec reflow time were then subjected to 160 C isothermal aging for up to 875 h. It was found that during reflow the Au layer reacted very quickly with the solder to form AuSn₄. One μm of Au layer was consumed in less than 10 sec. As the aging time increased, AuSn₄ grains began to separate themselves from the Ni layer at the roots of the grains and started to fall into the solder. When, the reflow time reached 30 sec, all the Au intermetallic head left the interface, and Ni₃Sn₄ started, to form at the interface. The Ni₃Sn₄ growth rate followed linear kinetics initially (<240 sec), but the growth rate slowed down afterward. During the isothermal aging, only a small amount of (Au_xNi_1-x)Sn₄ resettled back to the interface, and a continuous (Au_0.45Ni_0.55)Sn₄ layer did not form at the interface, unlike the case for the Sn-37Pb solder. This is an important advantage for Sn-3.5 Ag over Sn-37Pb because a continuous (Au_0.45Ni_0.55)Sn₄ layer inevitably will weaken a solder joint. Our observation indicated that many (Au_xNi_1-x)Sn₄ particles were trapped by the Ag₃Sn particles, and were hindered from resettling back to the interface.     

The first MAJC microprocessor: a dual CPU system-on-a-chip

The first implementation of MAJC architecture achieves high performance by using very long instruction word (VLIW), single instruction multiple data (SIMD), and chip multiprocessing. The chip integrates two processors, a memory controller, two high-speed parallel I/O interfaces, and a PCI controller. The chip, fabricated in a 0.22-μm CMOS process with six layers of copper interconnect, contains 13 million transistors and operates at 500 MHz. It is packaged in a 624-pin ceramic column grid array using flip-chip assembly technology     

甘油对中试魔芋葡甘聚糖流延膜性能的影响

目的解决可食性魔芋葡甘聚糖膜在连续化生产过程中出现的皱缩、易破损的问题。方法向魔芋葡甘聚糖料液中添加一定量的甘油,改善其平整度、柔韧性、拉伸性。结果当甘油添加量达到魔芋葡甘聚糖质量的25%时,制备出了皱缩率最低达0和断裂伸长率最高达65%的薄膜,该膜具有平整、透明度高以及拉伸性能好的特性。结论随着甘油添加量的增加,膜的皱缩率和拉伸强度降低;膜厚度、透明性、断裂伸长率和透湿系数增大。